One of the significant shortcomings of the contemporary power grid distribution systems, is that the systems do not know their own state. This is painfully felt during periods of massive failure caused by the fury of the elements or by a technical failure of a major component. Making power distribution networks robust and rapidly recoverable after natural disasters is perhaps the most urgent task in the on-going improvement of the national infrastructure. The importance of this task is generally understood. Its key elements include implementing modern monitor and control systems for power networks. These two systems must work coherently (with due regard for each other) with the monitor system setting the appropriate environment for the control system.
What is there to monitor, is an essential question. Each power distribution network can be described by a Graph represented by nodes of specified nature, their specified geographical position on a 2D map, and the topology of connecting lines. The state of the network is further characterized by the energy flow over the Graph.
Disruptions of the energy flow are associated with the breakdown of electrical connectivity of the power network and the required information that fully characterizes the network is therefore topological in nature. This is not, however, the shape in which the information about network failures reaches the control room of the contemporary utility. Instead of the desired automatic description of energy-flow disruptions, one deals with haphazard telephone reports of “no light in our house”. The price we pay is in delayed and low-efficiency repair activity.
Alternative approaches to automatic monitoring state of the power grid are as follows. A simple system could be based on “on-off” reports of local access to power, an automated sensor-based version of the customer telephone call. Even when such reports are fully collected and accurate, they provide no information needed for a topological analysis of the possibly impaired connectivity of the grid.
On the other hand, sophisticated systems may be based on phasor measurement units (PMU). The PMU are sometimes called the synchrophasors, as they measure the instantaneous values of both the voltage and the current synchronously over the network. A PMU network can be compared to a multi-channel digital oscilloscope with synchronized channels in different locations. This is an expensive proposition and to-date PMU installation has been limited to critical substations of a power grid. The use of PMU data presumes the preliminary knowledge of the network topology, which is justified only if the network is restricted to the backbone of principal intersecting locations.
The electrical grid monitor system (EGMS) discussed in the application is based on the modern sensor, communication and computational technologies. The EGMS will not tamper with the power networks themselves and it can be applied both to the existing grids and the future smart grids. The sensors to be used must be inexpensive and safe. The latter requirement precludes direct electrical contact with “hot” wires, so that the smart measurements should be based on sensing the magnetic field.
The approach of the invention to the EGMS aims at collecting the minimum data necessary to reconstruct the topological organization of the network. This makes the system inexpensive both in hardware and installation. The essential aspects of the invention that lead to this cost reduction are (i) abandoning instantaneous flow of data in favor of the average and (ii) eliminating all galvanic measurements, i.e. direct contact of sensors with the “hot” wire. Therefore, the EGMS can be contemplated to assume an utmost penetration of the power grid, down to single household units. The cost of individual sensors associated with the invention is substantially reduced. Such sensors can be installed and maintained by the relatively low level electric utility personnel, causing further cost reduction of installation and maintenance of the electrical grid monitor system of the invention.